Media and speed independent interface

ABSTRACT

A media and speed independent system for transmitting Ethernet data comprises a media access controller (MAC) and a first rate adaptation layer (RAL) module that communicates with the MAC. A first physical extension module communicates with the first RAL module. A second physical extension module communicates with the first physical extension module using a physical extension interface. A second RAL module communicates with the second physical extension module. A physical layer device (PHY) communicates with the second RAL module.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/114,842, filed Apr. 26, 2005 which claims the benefit of U.S.Provisional Application No. 60/640,529, filed on Dec. 30, 2004. Thedisclosure of the above application is incorporated herein by referencein its entirety.

FIELD OF THE INVENTION

The present invention relates to transmitting network data.

BACKGROUND OF THE INVENTION

Referring now to FIG. 1, a block diagram of a system 100 employing a 10Gbps media independent interface (XGMII) according to the prior art isdepicted. A switch 102 contains a media access controller (MAC) 104. TheMAC 104 communicates with a 10 Gbps physical layer device (PHY) 106within a PHY module 108 via an XGMII connection 110. The terms MAC, PHY,and many others are explained in IEEE Standard 802.3ae (30 Aug. 2002),which is incorporated herein by reference in its entirety. The XGMII isa simple and easy to implement interconnection between the switch 102and the PHY module 108, but it only supports a very limited connectiondistance between the switch 102 and PHY module 108. As such, a repeaterlayer that can extend the reach of XGMII was developed.

Referring now to FIG. 2, a system 130 according to the prior artcontains a switch 132 and a PHY module 134. Within the switch 132, a MAC136 communicates with a first XGMII extender sublayer (XGXS) module 138via an XGMII link 140. The first XGXS module 138 communicates with asecond XGXS module 142 via a 10 Gbps attachment unit interface (XAUI).The second XGXS module 142 communicates with a 10 Gbps PHY 146 via asecond XGMII link 148. XAUI allows the switch 132 and PHY 134 to have aconnection distance in the tens of inches, as compared to a limit ofapproximately 3 inches for an XGMII link (as in FIG. 1). The XGXSmodules, 138 and 142, translate between XGMII and XAUI. This allows thedesign of the MAC 136 and the PHY 146 to remain unchanged while stillachieving the extended reach of XAUI.

SUMMARY OF THE INVENTION

A rate adaptation layer (RAL) module for converting from a firstinterface operating at a first rate to a second interface operating at asecond rate comprises first and second input/output (I/O) modules thatcommunicate with the first and second interfaces, respectively. Arepeater module receives symbols from the first I/O module and transmitsthe symbols n times to the second I/O module, where n is determined bythe first and second rates. A pull-down module receives symbols from thesecond I/O module and selectively extracts symbols to be communicated tothe first I/O module.

In other features, the second rate is greater than or equal to the firstrate. The first rate is one of 10 Mbps, 100 Mbps, 1 Gbps, and 10 Gbps.The second rate is 10 Gbps. The repeater module stripes repeated symbolsacross four lanes. The repeater module begins striping symbols in one ofthe four lanes. A delimiter injection module communicates a start symbolto the second I/O module to indicate a packet beginning and a terminatesymbol to the second I/O module to indicate a packet ending. The secondI/O module communicates data symbols and the start and terminate symbolsto the second interface. The delimiter injection module replaces a datasymbol communicated from the repeater module to the second I/O modulewith the start symbol. The repeater module stripes repeated symbolsacross four lanes. At least one of the four lanes are selectivelydeactivated. Three of the four lanes are selectively deactivated.

In other features, the at least one of the four lanes are deactivatedwhen the first rate is less than the second rate. The delimiterinjection module selectively inserts idle symbols before the terminatesymbol to align the terminate and start symbols on the same one of thefour lanes. A carrier extend substitution module selectively replacessymbols received from the first I/O module before they are passed to therepeater module. The carrier extend substitution module replaces acarrier extend symbol with an idle symbol and a carrier extend/errorsymbol with a symbol error. n is equal to the second rate divided by thefirst rate.

In other features, a nibble replicator module selectively replaces eachfour-bit nibble received from the first I/O module with a bytecomprising two copies of the nibble, before passing the byte to therepeater module. The nibble replicator module is enabled when the firstrate is equal to one of 10 Mbps and 100 Mbps. n is equal to the secondrate divided by twice the first rate when the nibble replicator moduleis enabled, and equal to the second rate divided by the first rateotherwise. The pull-down module extracts one of x symbols, then one of ysymbols, in alternating succession. x is equal to a rounded up divisionof n by four, and wherein y is equal to a rounded down division of n byfour. The first I/O module inserts and removes idle symbols to retainclock synchronization with the first interface.

In other features, a media and speed independent device comprises theRAL module and further comprises a media access controller (MAC) thatcommunicates with the RAL module. A physical extension modulecommunicates with the RAL module and with the external device using aphysical extension interface. The physical extension interface includesa 10 Gbps attachment unit interface (XAUI) and the physical extensionmodule includes a 10 Gbps media independent interface (XGMII) extendersublayer (XGXS) module. The physical extension interface isbidirectional serial and the physical extension module includes a 10Gbps BASE-R (10 GBASE-R) module. The MAC communicates with the RALmodule using extended XGMII (EXGMII).

In still other features, a media and speed independent device comprisesthe RAL module and further comprises a physical layer device (PHY) thatcommunicates with the RAL module. A physical extension modulecommunicates with the RAL module and with the external device using aphysical extension interface. The physical extension interface includesa 10 Gbps attachment unit interface (XAUI) and the physical extensionmodule includes a 10 Gbps media independent interface (XGMII) extendersublayer (XGXS) module. The physical extension interface isbidirectional serial and the physical extension module includes a 10Gbps BASE-R (10 GBASE-R) module. The PHY communicates with the RALmodule using EXGMII.

A method for operating a rate adaptation layer (RAL) module comprisesproviding a first interface operating at a first rate and a secondinterface operating at a second rate; providing first and secondinput/output (I/O) modules that communicate with the first and secondinterfaces, respectively; receiving symbols from the first I/O module;transmitting the symbols n times to the second I/O module, where n isdetermined by the first and second rates; and selectively extractingsymbols to be communicated to the first I/O module.

In other features, the second rate is greater than or equal to the firstrate. The first rate is one of 10 Mbps, 100 Mbps, 1 Gbps, and 10 Gbps.The second rate is 10 Gbps. The method includes striping repeatedsymbols across four lanes. The method includes beginning stripingsymbols in one of the four lanes. The method includes communicating astart symbol to the second I/O module to indicate a packet beginning;and communicating a terminate symbol to the second I/O module toindicate a packet ending. In other features, the method includescommunicating data symbols and the start and terminate symbols to thesecond interface. The method includes replacing a data symbolcommunicated from the repeater module to the second I/O module with thestart symbol. The method includes striping repeated symbols across fourlanes. The method includes selectively deactivating at least one of thefour lanes to save power. The method includes selectively deactivatingthree of the four lanes. The method includes selectively deactivatingthe at least one of the four lanes when the first rate is less than thesecond rate.

In other features, the method includes selectively inserting idlesymbols before the terminate symbol to align the terminate and startsymbols on the same one of the four lanes. The method includesselectively replacing symbols received from the first I/O module beforethey are passed to the repeater module. The method includes replacing acarrier extend symbol with an idle symbol; and replacing a carrierextend/error symbol with a symbol error. n is equal to the second ratedivided by the first rate. The method includes selectively replacingeach four-bit nibble received from the first I/O module with a bytecomprising two copies of the nibble before passing the byte to therepeater module. The method includes extracting one of x symbols, thenone of y symbols, in alternating succession. x is equal to a rounded updivision of n by four, and wherein y is equal to a rounded down divisionof n by four. The method includes inserting and removing idle symbols toretain clock synchronization with the first interface.

A rate adaptation layer (RAL) module for converting from a firstinterface operating at a first rate to a second interface operating at asecond rate comprises first and second input/output (I/O) means forcommunicating with the first and second interfaces, respectively.Repeater means receives symbols from the first I/O means and transmitsthe symbols n times to the second I/O means, where n is determined bythe first and second rates. Pull-down means receives symbols from thesecond I/O means and selectively extracts symbols to be communicated tothe first I/O means.

In other features, the second rate is greater than or equal to the firstrate. The first rate is one of 10 Mbps, 100 Mbps, 1 Gbps, and 10 Gbps.The second rate is 10 Gbps. The repeater means stripes repeated symbolsacross four lanes. The repeater means begins striping symbols in one ofthe four lanes. Delimiter injection means communicates a start symbol tothe second I/O means to indicate a packet beginning, and communicates aterminate symbol to the second I/O means to indicate a packet ending.The second I/O means communicates data symbols and the start andterminate symbols to the second interface. The delimiter injection meansreplaces a data symbol communicated from the repeater means to thesecond I/O means with the start symbol.

In other features, the repeater means stripes repeated symbols acrossfour lanes. At least one of the four lanes are selectively deactivatedto save power. Three of the four lanes are selectively deactivated. Theat least one of the four lanes are deactivated when the first rate isless than the second rate. The delimiter injection means selectivelyinserts idle symbols before the terminate symbol to align the terminateand start symbols on the same one of the four lanes. Carrier extendsubstitution means selectively replaces symbols received from the firstI/O means before they are passed to the repeater means. The carrierextend substitution means replaces a carrier extend symbol with an idlesymbol, and replaces a carrier extend/error symbol with a symbol error.n is equal to the second rate divided by the first rate.

In other features, nibble replicating means for selectively replacingeach four-bit nibble received from the first I/O means with a bytecomprising two copies of the nibble, before passing the byte to therepeater means. The nibble replicator means is enabled when the firstrate is equal to one of 10 Mbps and 100 Mbps. n is equal to the secondrate divided by twice the first rate when the nibble replicator means isenabled, and equal to the second rate divided by the first rateotherwise. The pull-down means extracts one of x symbols, then one of ysymbols, in alternating succession. x is equal to a rounded up divisionof n by four, and wherein y is equal to a rounded down division of n byfour. The first I/O means inserts and removes idle symbols to retainclock synchronization with the first interface.

In other features, a media and speed independent device comprising theRAL module of and further comprises media access controller (MAC) meansfor communicating with the RAL means. Physical extension meanscommunicates with the RAL means and the external device using a physicalextension interface. The physical extension interface includes a 10 Gbpsattachment unit interface (XAUI) and the physical extension meansincludes a 10 Gbps media independent interface (XGMII) extender sublayer(XGXS) module. The physical extension interface is bidirectional serialand the physical extension means includes a 10 Gbps BASE-R (10 GBASE-R)module. The MAC means communicates with the RAL means using extendedXGMII (EXGMII).

In still other features, a media and speed independent device comprisingthe RAL module and further comprises physical layer (PHY) means forcommunicating with the RAL module. Physical extension means communicateswith the RAL module and with the external device using a physicalextension interface.

In other features, the physical extension interface includes a 10 Gbpsattachment unit interface (XAUI) and the physical extension meansincludes a 10 Gbps media independent interface (XGMII) extender sublayer(XGXS) module. The physical extension interface is bidirectional serialand the physical extension means includes a 10 Gbps BASE-R (10 GBASE-R)module. The PHY means communicates with the RAL means using EXGMII.

A media and speed independent system for transmitting Ethernet datacomprises a media access controller (MAC) and a first rate adaptationlayer (RAL) module that communicates with the MAC. A first physicalextension module communicates with the first RAL module. A secondphysical extension module communicates with the first physical extensionmodule using a physical extension interface. A second RAL modulecommunicates with the second physical extension module. A physical layerdevice (PHY) communicates with the second RAL module.

In other features, the physical extension interface includes a 10 Gbpsattachment unit interface (XAUI) and the first and second physicalextension modules include 10 Gbps media independent interface (XGMII)extender sublayer (XGXS) modules. The physical extension interfaceincludes bidirectional serial and the first and second physicalextension modules include 10 Gbps BASE-R (10 GBASE-R) modules. The MACcommunicates with the first RAL module using extended XGMII (EXGMII),and the PHY communicates with the second RAL module using EXGMII.

A media and speed independent device for transmitting Ethernet data toan external device comprises a media access controller (MAC) and a rateadaptation layer (RAL) module that communicates with the MAC. A physicalextension module communicates with the RAL module and with the externaldevice using a physical extension interface.

In other features, the physical extension interface includes a 10 Gbpsattachment unit interface (XAUI) and the physical extension moduleincludes a 10 Gbps media independent interface (XGMII) extender sublayer(XGXS) module. The physical extension interface includes bidirectionalserial and the physical extension module includes a 10 Gbps BASE-R (10GBASE-R) module. The MAC communicates with the RAL module using extendedXGMII (EXGMII).

A media and speed independent system for transmitting Ethernet datacomprises media access controller (MAC) means for providing a firstinterface. First rate adaptation layer (RAL) means communicates with theMAC means. First physical extension means communicates with the firstRAL means. Second physical extension means communicates with the firstphysical extension means using a physical extension interface. SecondRAL means communicates with the second physical extension means.Physical layer (PHY) means communicates with the second RAL means and amedium.

In other features, the physical extension interface includes a 10 Gbpsattachment unit interface (XAUI) and the first and second physicalextension means include 10 Gbps media independent interface (XGMII)extender sublayer (XGXS) modules. The physical extension interfaceincludes bidirectional serial and the first and second physicalextension means include 10 Gbps BASE-R (10 GBASE-R) modules. The MACmeans communicates with the first RAL means using extended XGMII(EXGMII), and the PHY means communicates with the second RAL means usingEXGMII.

A media and speed independent device for transmitting Ethernet data toan external device comprises media access controller (MAC) means forproviding an interface. Rate adaptation layer (RAL) means communicateswith the MAC means. Physical extension means communicates with the RALmeans and with the external device using a physical extension interface.

In other features, the physical extension interface includes a 10 Gbpsattachment unit interface (XAUI) and the physical extension meansincludes a 10 Gbps media independent interface (XGMII) extender sublayer(XGXS) module. The physical extension interface includes bidirectionalserial and the physical extension means includes a 10 Gbps BASE-R (10GBASE-R) module. The MAC means communicates with the RAL means usingextended XGMII (EXGMII).

A method for operating a media and speed independent system fortransmitting Ethernet data comprises providing a media access controller(MAC); providing a first rate adaptation layer (RAL) module thatcommunicates with the MAC; providing a first physical extension modulethat communicates with the first RAL module; providing a second physicalextension module that communicates with the first physical extensionmodule using a physical extension interface; providing a second RALmodule that communicates with the second physical extension module; andproviding a physical layer device (PHY) that communicates with thesecond RAL module.

In other features, the physical extension interface includes a 10 Gbpsattachment unit interface (XAUI) and the first and second physicalextension modules include 10 Gbps media independent interface (XGMII)extender sublayer (XGXS) modules. The physical extension interface isbidirectional serial and the first and second physical extension modulesinclude 10 Gbps BASE-R (10 GBASE-R) modules. The method includes usingextended XGMII (EXGMII) for communication between the MAC and the firstRAL module; and using EXGMII for communication between the PHY and thesecond RAL module.

A method for operating a media and speed independent device fortransmitting Ethernet data to an external device comprises providing amedia access controller (MAC); providing a rate adaptation layer (RAL)module that communicates with the MAC; and providing a physicalextension module that communicates with the RAL module and thatcommunicates with the external device using a physical extensioninterface.

In other features, the physical extension interface is a 10 Gbpsattachment unit interface (XAUI) and the physical extension module is a10 Gbps media independent interface (XGMII) extender sublayer (XGXS)module. The physical extension interface is bidirectional serial and thephysical extension module includes a 10 Gbps BASE-R (10 GBASE-R) module.The method includes using extended XGMII (EXGMII) for communicationbetween the MAC and the RAL module.

A media and speed independent device for transmitting Ethernet data toan external device comprises a physical layer device (PHY) and a rateadaptation layer (RAL) module that communicates with the PHY. A physicalextension module communicates with the RAL module and with the externaldevice using a physical extension interface.

In other features, the physical extension interface is a 10 Gbpsattachment unit interface (XAUI) and the physical extension module is a10 Gbps media independent interface (XGMII) extender sublayer (XGXS)module. The physical extension interface is bidirectional serial and thephysical extension module is a 10 Gbps BASE-R (10 GBASE-R) module. ThePHY communicates with the RAL module using EXGMII.

A media and speed independent means for transmitting Ethernet data to anexternal device comprises physical layer (PHY) means for providing aninterface to a medium. Rate adaptation layer (RAL) means communicateswith the PHY means. Physical extension means communicates with the RALmeans and with the external device using a physical extension interface.

In other features, the physical extension interface includes a 10 Gbpsattachment unit interface (XAUI) and the physical extension meansincludes a 10 Gbps media independent interface (XGMII) extender sublayer(XGXS) module. The physical extension interface includes bidirectionalserial and the physical extension means includes a 10 Gbps BASE-R (10GBASE-R) module. The PHY communicates with the RAL means using EXGMII.

A method for communicating network data of varying speeds comprisesestablishing a plurality of signal interconnections; defining a firstmapping of XGMII signals onto the plurality of signal interconnections;defining a second mapping of GMII signals onto the plurality of signalinterconnections; and defining a third mapping of MII signals onto theplurality of signal interconnections.

In other features, the first mapping is a one to one mapping. Theplurality of signal interconnections includes a transmit set of signalinterconnections and a receive set of signal interconnections. Thefirst, second, and third mappings include mapping transmit data signalsto a set of the data signal interconnections of the transmit set. Thefirst, second, and third mappings include mapping receive data signalsto a set of the data signal interconnections of the receive set. Thefirst, second and third mappings include mapping transmit controlsignals to a set of control signal interconnections of the transmit set.The first, second and third mappings include mapping receive controlsignals to a set of control signal interconnections of the receive set.The first, second and third mappings include mapping a receive clocksignal to a clock signal interconnection of the receive set. The firstand second mappings involve mapping a transmit clock signal to a clocksignal interconnection of the transmit set. The third mapping involvesmapping a transmit clock signal to the clock signal interconnection ofthe transmit set. The third mapping involves mapping a transmit clocksignal to one of the data signal interconnections of the receive set.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a block diagram of system employing a 10 Gbps mediaindependent interface (XGMII) according to the prior art;

FIG. 2 is a block diagram of a system according to the prior artcontains a switch and a PHY module;

FIG. 3 is a block diagram of a system using a serial link to connect aswitch and PHY;

FIG. 4 is a mapping table of MII, GMII, and XGMII signals onto EXGMIIpins;

FIG. 5 is a block diagram of a system having an exemplary speed andmedia independent interface;

FIG. 6 is a block diagram of an alternative system using anotherexemplary interconnection according to the principals of the presentinvention;

FIG. 7 is a block diagram of an exemplary implementation of a rateadaptation layer (RAL) module;

FIG. 8 is a graphical depiction of exemplary byte striping across XGMIIlanes;

FIG. 9 is a table depicting byte striping on XGMII at the end of apacket; and

FIG. 10 is a table depicting byte striping across XGMII at the end of analternate packet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiments is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses. For purposes of clarity, the same referencenumbers will be used in the drawings to identify similar elements. Asused herein, the term module, controller and/or device refers to anapplication specific integrated circuit (ASIC), an electronic circuit, aprocessor (shared, dedicated, or group) and memory that execute one ormore software or firmware programs, a combinational logic circuit,and/or other suitable components that provide the describedfunctionality.

Referring now to FIG. 3, a system 160 according to the present inventionthat uses a serial link to connect a switch and PHY is illustrated. AMAC 162 within a switch 164 communicates with a 10 Gbps base R (10GBASE-R) module 166 via first XGMII link 168. The 10 GBASE-R module 166communicates with a second 10 GBASE-R module 170 via a serial link 172.The second 10 GBASE-R module 170 is located within a PHY module 174 andcommunicates with a 10 Gbps PHY 176 via a second XGMII link 178. Thissystem 160 essentially uses a 10 Gbps serial Ethernet connection betweenthe switch 164 and the PHY module 174. Although the serial link does notafford much greater distance than an XGMII link, the PHY module 174 canbe used to convert between electrical and optical media.

Because many MACs and PHYs are capable of supporting different speeds,it would be advantageous for the media independent interface (MII) toalso be speed independent so that the same MII could be used regardlessof the speed of the MAC or of the PHY. Additionally, it would bebeneficial for the design of the XGXS and the XAUI to remain unchangedand yet still transmit data at any speed supported by the MAC and thePHY.

A media independent interface (MII) is defined for transmitting 10 Mbpsdata and 100 Mbps data. A 1 Gbps MII (GMII) is defined to transmit 1Gbps Ethernet data, and a 10 Gbps MII (XGMII) is defined to transmit 10Gbps Ethernet data. Using three separate Mils to support transmission ofthe four speeds of Ethernet data is redundant. To reduce this waste, anextended XGMII (EXGMII) has been developed. In some implementations, theEXGMII uses the same number of signal interconnections (pins, traces,etc.) as XGMII, and accommodates XGMII, GMII, and MII.

Referring now to FIG. 4, a mapping of MII, GMII, and XGMII signals ontoEXGMII pins is shown. A mapping table 200 contains six columns. A firstcolumn 202 lists EXGMII pin names. A second column 204 specifies thetransmission direction with respect to the PHY. A third column 206specifies the XGMII signals that map to the corresponding EXGMII pin,which is indicated in the first column 202. A fourth column 208specifies the GMII signals that map to the corresponding EXGMII pin,which is indicated in the first column 202. A fifth column 210 specifiesthe MII signals that map to the corresponding EXGMII pin, which isindicated in the first column 202. A sixth column 212 specifies analternative mapping of MII signals to EXGMII pins. The alternativemapping in the sixth column 212 allows the transmit direction to besource-synchronous by making TX_CLK an input to the PHY (providing theclock for the input TXD data signals).

Referring now to FIG. 5, a system 300 having an exemplary speed andmedia independent interface is depicted. A switch 302 includes a mediaaccess controller (MAC) 304, a MAC rate adaptation layer (RAL) 306, anda first XGMII extender sublayer (XGXS) module 308. The MAC 304communicates with the MAC RAL 306 via an EXGMII link 310. The MAC RAL306 communicates with the first XGXS module 308 via an XGMII link 312. Aphysical layer device (PHY) 320 module contains a multispeed PHY 322, aPHY rate adaptation layer (RAL) 324, and a second XGXS module 326. ThePHY 322 communicates with the PHY RAL 324 via an EXGMII link 328. ThePHY RAL 324 communicates with the second XGXS module 326 via an XGMIIlink 330.

The first and second XGXS modules, 308 and 326, communicate via a 10Gbps Attachment Unit Interface (XAUI) 332. While the PHY 322 and the MAC304 can operate at a number of speeds (including 10 Mbps, 100 Mbps, 1Gbps, and 10 Gbps), the XGXS modules, 308 and 326, and the XAUI link 332operate at 10 Gbps. The RALs 306 and 324 convert from the line speed to10 Gbps. In this way the XGXS modules and the XAUI protocol can be usedwithout redesign.

Referring now to FIG. 6, a block diagram of an alternative system 350using another exemplary interconnection according to the principals ofthe present invention is depicted. The alternative system 350 is thesame as the system 300 of FIG. 5, except that the XGXS modules, 308 and326, have been replaced with 10 Gbps BASE-R (10 GBASE-R) modules, 352and 354, which communicate via a serial link 356. The 10 GBASE-Rmodules, 352 and 354, essentially form a 10 Gbps Ethernet link betweenthe switch 302 and PHY module 320.

Referring now to FIG. 7, a block diagram of an exemplary implementationof a rate adaptation layer (RAL) module is depicted. A system 400includes a RAL module 402 that communicates on one side with EXGMII andon the other with XGMII. A first input module 404 and a first outputmodule 406 communicate with EXGMII. A second input module 408 and asecond output module 410 communicate with XGMII. The first input module404 communicates with a carrier extend substitution module 412. Thecarrier extend substitution module 412 communicates an output to anibble replicator 416. The nibble replicator 416 communicates an outputto a repeater module 418. The repeater module 418 communicates an outputto a delimiter injection module 420. The delimiter injection module 420communicates an output to the second output module 410.

The second input module 408 communicates with a pull-down module 422.The pull-down module 422 communicates an output to the first outputmodule 406. A data rate value 424 is communicated to the carrier extendsubstitution module 412, the nibble replicator 416, the repeater module418, the delimiter injection module 420, and the pull-down module 422.

The carrier extend substitution module 412 operates when the rate 424 is1 Gbps. When operating, the carrier extend substitution module 412replaces a carrier extend symbol received from the first input module404 with an idle symbol, and replaces a carrier extend/error symbol witha symbol error. Otherwise, the carrier extend substitution module 412passes symbols unchanged. The nibble replicator 416 is enabled when therate 424 is either 10 Mbps or 100 Mbps. When enabled, the nibblereplicator 416 takes each received 4-bit nibble and duplicates it toform a byte. For example, a nibble 1011 will become the byte 10111011.

The repeater module 418 is inactive (pass-through) when the rate 424 is10 Gbps. When the rate 424 is 1 Gbps, the repeater module 418 willrepeat each received 8-bit data symbol ten times. The way in which theserepeated symbols are transmitted to the delimiter injection module 420is discussed below in conjunction with FIGS. 8 through 10. When the rate424 is 100 Mbps, the repeater module 418 repeats each byte fifty times.When the rate 424 is 10 Mbps, the repeater module 418 repeats each bytefive hundred times. The repeated symbols that the repeater module 418produces are striped across four lanes as XGMII specifies. As with therepeater module 418, the delimiter injection module 420 operates whenthe rate 424 is not 10 Gbps. The delimiter injection module 420 places a/S/ start symbol on lane zero at the beginning of a packet, and a /T/terminate symbol on lane zero immediately after the end of a packet. Anybytes between the end of the packet and the concluding /T/symbol arefilled with a pad byte.

The first and second input modules, 404 and 408, and first and secondoutput modules, 406 and 410, can be responsible for inserting andremoving idle symbols to match internal clock rates with that of theXGMII and EXGMII links. FIFO (first-in first-out) buffers used forinserting and removing idle symbols can be made smaller when only thefirst input module 404 and the first output module 406 are responsiblefor idle insertion and removal. The pull-down module 422 operates whenthe rate 424 is not 10 Gbps. The operation of the pull-down module 422will become more clear after FIGS. 8 through 10 are discussed.

Referring now to FIG. 8, a graphical depiction 500 of exemplary bytestriping across XGMII lanes is presented. Four XGMII lanes are numbered0 through 3. Idles 502 appear before the beginning of a packet. Thisexample is for an EXGMII link operating at 1 Gbps, and so bytes arerepeated ten times. Bytes are striped, beginning with lane 0 andprogressing through lane 3. For example, byte 0 (denoted B_(o)) startsin column 504, and continues through column 506 and half of column 508,where the next ten replicated bytes (B₁) begin. The first instance ofB_(o) (the start of a packet) is replaced with the /S/ start symbol 510(shown shaded). Striping for a packet begins on lane 0, and so the /S/symbol will always occur on lane 0. Inspecting lane 0 by itself, it canbe seen that bytes are presented in a 3-2-3-2 order. This is becausefour divides into ten 2.5 times. In order to decode the byte striping,only lane 0 need be inspected, and 1 byte selected from each of the 3-or 2-byte groups.

FIG. 9 is a table 530 depicting byte striping on XGMII at the end of apacket. The example of table 530 is also for a 1 Gbps EXGMII rate, andin this table the number of bytes in the packet is even. This means thata /T/ terminate symbol 532 placed after the last byte of the packet willnaturally fall on lane 0. The remaining three lanes are filled with idlesymbols.

Referring now to FIG. 10, a table 560 depicts byte striping across XGMIIat the end of an alternative packet. Here, the EXGMII rate is still 1Gbps, but the number of bytes in the packet is odd. With an odd numberof packets, a /T/ terminate symbol placed at the end of the data byteswill naturally fall in lane 2. For ease of recovery, however, the /T/terminate symbol should be placed on lane 0. To this end, two padsymbols 562 are inserted on lanes 2 and 3, which then causes the /T/terminate symbol 564 to fall on lane 0. As can be seen, the bytes of apacket can be decoded by looking only at lane 0. This means that lanes 1through 3 may be turned off to save power when not operating at 10 Gbps.

Returning now to FIG. 7, operation of the pull-down module 422 is moreclear. The pull-down module 422 simply passes data through when the rate424 is 10 Gbps. When the rate 424 is 1 Gbps, the pull-down module 422extracts from XGMII lane 0 one of three bytes, one of two bytes, one ofthree bytes, one of two bytes, and so on. When the rate 424 is 100 Mbps,recall that bytes were replicated fifty times. Four divides into fifty12.5 times, and therefore the pull-down module 422 will extract one ofthirteen bytes, one of twelve bytes, one of thirteen bytes, one oftwelve bytes, and so on. In 10 Mbps mode, recall that bytes werereplicated five hundred times. Four divides evenly into five hundred 125times, and therefore the pull-down module 422 extracts one byte out ofevery 125 bytes received.

Those skilled in the art can now appreciate from the foregoingdescription that the broad teachings of the present invention can beimplemented in a variety of forms. Therefore, while this invention hasbeen described in connection with particular examples thereof, the truescope of the invention should not be so limited since othermodifications will become apparent to the skilled practitioner upon astudy of the drawings, the specification and the following claims.

1. A media and speed independent system for transmitting data,comprising: a media access controller (MAC); a first rate adaptationlayer (RAL) module that communicates with said MAC using an extended 10Gbps media independent interface (EXGMII); a first physical extensionmodule that communicates with said first RAL module; a second physicalextension module that communicates with said first physical extensionmodule using a physical extension interface; a second RAL module thatcommunicates with said second physical extension module; and a physicallayer device (PHY) that communicates with said second RAL module usingsaid EXGMII, wherein said EXGMII includes a plurality of signals thatare mapped to signals of a media independent interface (MII), signals ofa 1 Gbps MII (GMII), and signals of a 10 Gbps MII (XGMII).
 2. The systemof claim 1 wherein said physical extension interface includes a 10 Gbpsattachment unit interface (XAUI) and said first and second physicalextension modules include XGMII extender sublayer (XGXS) modules.
 3. Thesystem of claim 1 wherein said physical extension interface isbidirectional serial and said first and second physical extensionmodules include 10 Gbps BASE-R (10 GBASE-R) modules.
 4. The system ofclaim 1 wherein said signals of said XGMII have a one-to-onecorrespondence with said plurality of signals.
 5. The system of claim 4wherein said signals of said GMII have a one-to-one correspondence witha first subset of said plurality of signals, wherein said signals ofsaid MII have a one-to-one correspondence with a second subset of saidplurality of signals, and wherein ones of said plurality of signals areincluded in both said first subset of said plurality of signals and saidsecond subset of said plurality of signals.
 6. The system of claim 4wherein said plurality of signals have a one-to-one correspondence witha plurality of physical conductors, wherein said signals of said GMIIhave a one-to-one correspondence with a first subset of said pluralityof physical conductors, and wherein said signals of said MII have aone-to-one correspondence with a second subset of said plurality ofphysical conductors.
 7. A media and speed independent system fortransmitting Ethernet data, comprising: media access controller (MAC)means for providing a first interface; first rate adaptation layer (RAL)means for communicating with said MAC means using an extended 10 Gbpsmedia independent interface (EXGMII); first physical extension means forcommunicating with said first RAL means; second physical extension meansfor communicating with said first physical extension means using aphysical extension interface; second RAL means for communicating withsaid second physical extension means; and physical layer (PHY) means forcommunicating with said second RAL means using said EXGMII, wherein saidEXGMII includes a plurality of signals that are mapped to signals of amedia independent interface (MII), signals of a 1 Gbps MII (GMII), andsignals of a 10 Gbps MII (XGMII).
 8. The system of claim 7 wherein saidphysical extension interface includes a 10 Gbps attachment unitinterface (XAUI) and said first and second physical extension meansinclude XGMII extender sublayer (XGXS) modules.
 9. The system of claim 7wherein said physical extension interface is bidirectional serial andsaid first and second physical extension means include 10 Gbps BASE-R(10 GBASE-R) modules.
 10. The system of claim 7 wherein said signals ofsaid XGMII have a one-to-one correspondence with said plurality ofsignals.
 11. The system of claim 10 wherein said signals of said GMIIhave a one-to-one correspondence with a first subset of said pluralityof signals, wherein said signals of said MII have a one-to-onecorrespondence with a second subset of said plurality of signals, andwherein ones of said plurality of signals are included in both saidfirst subset of said plurality of signals and said second subset of saidplurality of signals.
 12. The system of claim 10 wherein said pluralityof signals have a one-to-one correspondence with a plurality of physicalconductors, wherein said signals of said GMII have a one-to-onecorrespondence with a first subset of said plurality of physicalconductors, and wherein said signals of said MII have a one-to-onecorrespondence with a second subset of said plurality of physicalconductors.
 13. A method for operating a media and speed independentsystem for transmitting data, comprising: providing a media accesscontroller (MAC); providing a first rate adaptation layer (RAL) module;transmitting data between said MAC and said first RAL module using anextended 10 Gbps media independent interface (EXGMII); providing a firstphysical extension module; transmitting data between said first physicalextension module and said first RAL module using a 10 Gbps mediaindependent interface (XGMII); providing a second physical extensionmodule; transmitting data between said second physical extension moduleand said first physical extension module using a physical extensioninterface; providing a second RAL module; transmitting data between saidsecond RAL module and said second physical extension module using saidXGMII; providing a physical layer device (PHY); and transmitting databetween said PHY and said second RAL module using said EXGMII, whereinsaid EXGMII includes a plurality of signals that are mapped to signalsof a media independent interface (MII), signals of a 1 Gbps MII (GMII),and signals of said XGMII.
 14. The method of claim 13 wherein saidphysical extension interface includes a 10 Gbps attachment unitinterface (XAUI) and said first and second physical extension modulesinclude XGMII extender sublayer (XGXS) modules.
 15. The method of claim13 wherein said physical extension interface is bidirectional serial andsaid first and second physical extension modules include 10 Gbps BASE-R(10 GBASE-R) modules.
 16. The method of claim 13 wherein said signals ofsaid XGMII have a one-to-one correspondence with said plurality ofsignals.
 17. The method of claim 16 wherein said signals of said GMIIhave a one-to-one correspondence with a first subset of said pluralityof signals, wherein said signals of said MII have a one-to-onecorrespondence with a second subset of said plurality of signals, andwherein ones of said plurality of signals are included in both saidfirst subset of said plurality of signals and said second subset of saidplurality of signals.
 18. The method of claim 16 wherein said pluralityof signals have a one-to-one correspondence with a plurality of physicalconductors, wherein said signals of said GMII have a one-to-onecorrespondence with a first subset of said plurality of physicalconductors, and wherein said signals of said MII have a one-to-onecorrespondence with a second subset of said plurality of physicalconductors.